The present invention relates to a heating element cooling structure and a drive device having the cooling structure.
When an electric motor is used as a driving power source of a vehicle, the electric motor requires an inverter for controlling the electric motor and an ECU or the like for controlling the inverter. The inverter and the like are each connected to the electric motor via a power cable. Thus, it is possible to position these elements in appropriate places away from the electric motor. However, for the sake of convenience during the installation of these elements into the vehicle, these elements may be arranged to be integrated with a drive unit that has the electric motor built therein.
The heat resistance temperature of the inverter and the like is currently lower than the heat resistance temperature of the electric motor. Thus, when the inverter and the like are positioned so as to be integrated with the drive unit that has the electric motor built therein, it is necessary to have an arrangement for blocking the heat that is directly transferred from the electric motor to the inverter and the like in order to thermally protect the inverter and the like. In addition, because the temperature of the inverter and the like increases due to their own heat generation, it is necessary to cool down the inverter and the like so that they are kept below their heat resistance temperatures.
To cope with this circumstance, a drive unit that has a cooling structure for cooling down an inverter as well as an electric motor has conventionally been proposed (for example, see International Publication No. WO 2004/025807). In the cooling structure included in the drive unit disclosed in International Publication No. WO 2004/025807, a coolant space is formed between a heat releasing surface that is thermally connected to an inverter and an opposing surface that is positioned opposite the heat releasing surface and is thermally connected to the drive unit case. A plurality of heat releasing fins are provided within the coolant space such that they are positioned parallel to one another and stand from the heat releasing surface on the inverter case side toward the case surface on the drive unit case side. An inter-fin passage through which a coolant flows is formed between every two of the plurality of heat releasing fins that are positioned adjacent to each other. In this type of cooling structure, the coolant that is supplied by a coolant pump into the coolant space flows through the plurality of inter-fin passages that are positioned parallel to one another. With this arrangement, it is possible to cool down the inverter via the heat-releasing surface and also to cool down the electric motor via the opposing surface.
Also, Japanese Patent Application Publication No. JP-A-2001-35981 discloses a cooling structure that is similar to the cooling structure disclosed in International Publication No. WO 2004/025807. In the cooling structure disclosed in Japanese Patent Application Publication No. JP-A-2001-35981, ends of inter-fin passages on one side are connected to one another to allow communication there between by a first header that is substantially as high as heat releasing fins. Ends of inter-fin passages on the other side are connected to one another to allow communication there between by a second header that has the same configuration as the first header. In this cooling structure, coolant that is supplied to the first header is distributed so as to flow through each of the inter-fin passages. The coolant that has flowed out of the inter-fin passages meets at the second header.